I don't get it. What does the selective coloring accomplish here? You say that it forces a focal point, but I'm not really seeing it. The radio tower (?) is arguably reinforced slightly, but it's still lost in the muddle of the skyline.
I agree with the radio tower comment, but it's already so seperate from the rest, of course putting it against a black/grey BG will make it "pop"... but I don't think it helps the photo as a whole, either.
So, OP, is it contrast your looking to add to this? Have you played with curves? Or maybe add a gradient to your sky to make it a bit more interesting? Just throwing ideas out